In the field of high temperature sensing, it is well known to use dissimilar metals or alloys which have a junction located close to the point where the temperature is to be sensed. The high temperature produces a thermoelectric potential at the junction between the two dissimilar metals and this thermoelectric voltage may be sensed, amplified, and employed as an indication of the temperature being sensed, in view of the increase in the thermoelectric effect with increased temperature. Two well known alloys which are used in high temperature thermocouples are chromel and alumel. In practice it is desirable that the entire circuit extending from the sensing junction back to the relatively cooler point where the electronics are located be formed of the same two thermocouple materials, chromel and alumel; and this would include the thermocouple wires themselves, the terminal at each thermocouple junction, and the heavy electrical conductors or busses which extend back to the electronic circuit. Then, within the electronic circuitry, conventional "cold junction temperature compensation" circuitry is employed, and the thermoelectric current or voltage is accurately calibrated to indicate the temperature at the thermocouple junction. A number of different forms of thermocouple housing assemblies have been proposed heretofore, and one such arrangement is disclosed in U.S. Pat. No. 4,460,225, assigned to the assignee of the present invention, and other known arrangements are shown in the patents cited in that issued patent.
Many thermocouples which have been proposed heretofore have been relatively heavy and massive, and therefore have not been suitable for certain applications where weight is an important factor. In addition, certain prior thermocouples have not been as rugged, or have as fast a response as might be desirable. Other thermocouples have been limited in the temperatures to which they may be reliably employed.
Accordingly, objects of the present invention include (1) a reduction in the weight of thermocouple assemblies; (2) providing increased ruggedness at high temperatures; (3) increasng the speed of response of thermocouples without significantly decreasing their mechanical strength, and (4) simplifying assembly of thermocouple units, by eliminating the brazing or welding steps which have been used heretofore.